1. Field of the Invention
This invention relates to media adjustment guides for media supply trays commonly incorporated in image forming devices such as copy machines and printers. More particularly, it relates to adjustment guides which can be injection molded from polymeric organic compounds, such as plastic materials.
2. Description of Related Art
When loading printing media, such as sheets of paper or transparencies, into a media supply tray of an image forming device such as a copy machine, printer or facsimile machine, it is generally easier to adjust the position of the media guide(s) once the media is in place. This is particularly true when the media is of nonstandard size. Presently, the media guides of most media trays require adjustment prior to loading the media. Damage to the media is a likely result if the order is reversed. In addition, many guides permit adjustment to only standard media sizes. The use of nonstandard size media may cause misfeeds or misaligned placement of the image on the media. Some guides, although designed to provide infinite adjustment, are relatively complicated and costly, in addition to being difficult to operate. If such a guide requires adjustment prior to loading of the media, the user must know the size of the media in order to avoid a hit-and-miss approach. Other guides, though designed to provide infinite adjustment after the media has been loaded, are maintained in the set position by friction. Such a guide may shift during operation, causing misfeeding of the media, media jams in the copying/printing device, or misalignment of the printed image.
The design of prior-art guide-adjustment mechanisms will now be briefly discussed. Certain guides employ a rack and pawl design. When the rack ad pawls are fabricated from plastic materials, tooth pitch on the rack must be sufficiently coarse to prevent rapid wear or shearing of the rack teeth. A coarse rack pitch prevents fine adjustment of the guide. Often, tooth pitch of such designs is set for standard media sizes, resulting in poor guide positioning for nonstandard media sizes. Other media guides are removably inserted in locating holes. Such guides may be repositioned to various other locations equipped with locating holes. However, the locating holes provide positioning of the guide for only standard media sizes, and the guide must generally be set in the proper position prior to loading the media. Some guides are designed to permit infinite adjustment, but adjustment is relatively awkward. One such design requires the user to squeeze two parts of the guide together to release the guide, and then slide the guide in a direction that is perpendicular to the squeezing motion.
What is needed is a media tray incorporating a media guide having a durable mechanism which provides for fine-pitch adjustments, and which may be fabricated from relatively soft polymeric plastic compounds.